1. Field of the Invention
The invention relates to a module for an optical device suitable for a camera module and the like for capturing an image of an object, and to a manufacturing method therefor.
2. Description of Related Art
A portable electronic apparatus such as a cellular phone or the like has recently been equipped with a camera function, so that a module for an optical device such as a camera module has been developed (for example, see Japanese Patent Application Laid-Open No. 2002-182270).
FIG. 1 is a schematic view showing a section of a conventional module for an optical device. Reference numeral 30 denotes a wiring substrate 30 which has conductive wirings 31 patterned on its surface (both surfaces). The conductive wirings 31 formed on both surfaces of the wiring substrate 30 are appropriately connected to each other within the wiring substrate 30. A DSP (Digital Signal Processor) 32 is die-bonded to one side (a surface on which a lens 37 described later is placed: this surface will be hereinafter referred to as an upper surface) of the wiring substrate 30. Each connecting terminal of the DSP 32 is electrically connected to the conductive wiring 31 by a bonding wire 32w. Bonded on the upper surface of the DSP 32 is a spacer 33 that is a sheet-shaped insulative adhesive. A solid-state image sensor 34 is die-bonded on the upper surface of the spacer 33. Each connecting terminal of the solid-state image sensor 34 is electrically connected to the conductive wiring 31 by a bonding wire 34w. 
Reference numeral 37 denotes an objective lens which is held at the inner peripheral portion of a focus adjuster 36. The focus adjuster 36 is provided at the inner peripheral portion close to the upper end portion of a lens holder main body 35. The lens holder main body 35 is formed such that its lower end portion is widened rather than its upper end portion. The widened lower end portion of the lens holder main body 35 is bonded to the peripheral portion of the wiring substrate 30. The focus adjuster 36 is threaded at its outer periphery, and the lens holder main body 35 is also threaded at its inner periphery close to its upper end portion. The threaded outer periphery of the focus adjuster 36 is screwed onto the threaded inner periphery close to the upper end portion of the lens holder main body 35. Accordingly, it is configured such that pivotable rotation of the focus adjuster 36 changes the mutual position, i.e., the distance between the lens 37 and the solid-state image sensor 34. It is noted that the lens holder main body 35 and the focus adjuster 36 form a lens holder for holding the lens 37. Specifically, the lens 37 is positioned by the lens holder (lens holder main body 35, focus adjuster 36) with (the surface of) the wiring substrate 30 defined as a positioning reference. Bonded to the lens holder main body 35 is an optical filter 38 that is subject to filtering treatment for cutting infrared rays in incident ray.
There may be a case where the size (especially the size in the thickness direction) of the wiring substrate 30 has a warp, distortion or the like due to variations in production, even if it is within the range of the specification value. Even after the lens holder main body 35 is bonded, such warp or distortion is present on the wiring substrate 30. Specifically, upon positioning the lens 37, there may be the case where the optical distance between the lens 37 and the solid-state image sensor 34 does not agree with the focal length f of the lens 37 due to the warp or the like on (the surface of) the wiring substrate 30 that is a positioning reference. In this case, the optical distance between the lens 37 and the solid-state image sensor 34 is required to be adjusted so as to agree with the focal length f of the lens 37. In other words, the optical distance between the lens 37 and the solid-state image sensor 34 is required to be adjusted so as to agree with the focal length f of the lens 37 by pivotably rotating the focus adjuster 36. Accordingly, the module for an optical device is finally completed by adjusting the relative position of the focus adjuster 36 to the lens holder main body 35.
FIG. 2 through FIG. 4 are schematic views each showing a section for explaining a problem of a conventional module for an optical device. FIG. 2 is a schematic view showing a case where the center portion of the wiring substrate 30 is formed into a convex shape toward the lens 37. Although the parallel relationship between the lens 37 and the wiring substrate 30 is maintained, the peripheral portion of the wiring substrate 30 is warped toward the direction apart from the lens 37, compared to its center portion. Therefore, the lens holder main body 35 whose widened lower end portion is bonded to the peripheral portion of the wiring substrate 30 is downwardly moved (in the direction apart from the lens 37) with respect to the center portion of the wiring substrate 30. This means that the positioning reference for the lens 37 is moved downward. Specifically, the optical distance between the lens 37 and the solid-state image sensor 34 becomes f−Δf (Δf is an amount of deformation of the wiring substrate 30 at the peripheral portion with respect to the center portion in the thickness direction), that is different from the focal length f of the lens 37. Accordingly, it is required to agree the solid-state image sensor 34 with the position of the focal length f of the lens 37 by performing an adjustment corresponding to the deformation amount Δf with the focus adjuster 36, i.e., by performing an adjustment for separating the solid-state image sensor 34 from the lens 37, in the state shown in FIG. 2.
FIG. 3 is a schematic view showing a case where the center portion of the wiring substrate 30 is formed into a concave shape toward the lens 37. Although the parallel relationship between the lens 37 and the wiring substrate 30 is maintained, the peripheral portion of the wiring substrate 30 comes close to the lens 37, compared to its center portion. Therefore, the lens holder main body 35 whose widened lower end portion is bonded to the peripheral portion of the wiring substrate 30 is upwardly moved (in the direction of coming close to the lens 37) with respect to the center portion of the wiring substrate 30. This means that the positioning reference for the lens 37 is moved upward. Specifically, the optical distance between the lens 37 and the solid-state image sensor 34 becomes f+Δf (Δf is an amount of deformation of the wiring substrate 30 at the peripheral portion with respect to the center portion in the thickness direction), that is different from the focal length f of the lens 37. Accordingly, it is required to agree the solid-state image sensor 34 with the position of the focal length f of the lens 37 by performing an adjustment corresponding to the deformation amount Δf with the focus adjuster 36, i.e., by performing an adjustment for making the solid-state image sensor 34 close to the lens 37, in the state shown in FIG. 3.
FIG. 4 is a schematic view showing a case where the plate thickness of the wiring substrate 30 is not uniform. In the example shown in FIG. 4, the thickness is great at the right-side end portion (right end in the figure) of the wiring substrate 30, while the thickness is small at the left-side end portion (left end in the figure) thereof. Assuming that the plane shape of the wiring substrate 30 is a rectangular, each side having approximately 10 mm, and the difference of the thickness between at the opposing ends of the wiring substrate 30 is ±0.01 mm in case where the thickness of the wiring substrate 30 is different at the opposing ends. Even if the thickness itself of the wiring substrate 30 is within the specification, the lens holder main body 35 and the focus adjuster 36 are fixed so as to be inclined with respect to the surface (plane) of the solid-state image sensor 34 when the lens holder main body 35 is bonded to the wiring substrate 30. When the lens holder main body 35 and the focus adjuster 36 are fixed so as to be inclined with respect to the surface of the solid-state image sensor 34, a deviation of an angle θ occurs between the optical axis of the lens 37 and the vertical axis of the solid-state image sensor 34, thereby incapable of correctly projecting an image of a subject onto the solid-state image sensor 34.
As described above, in the conventional optical device module, (the surface of) the wiring substrate 30 is defined as the positioning reference for the lens and the lens holder (optical path demarcating unit, focus adjuster) is bonded to the wiring substrate 30. Therefore, there may be the case where the optical distance between the lens 37 and the solid-state image sensor 34 does not agree with the focal length of the lens 37 due to variations in production such as warp or distortion on the wiring substrate 30 and, further, there is a problem that the optical axis of the lens 37 and the vertical axis of (the surface of) the solid-state image sensor 34 do not agree with each other. Therefore, an adjusting process is inevitable for matching the optical distance between the lens 37 and the solid-state image sensor 34 with the focal length of the lens 37 for each module for an optical device. In this adjusting process, an expensive system for the adjustment and a skilled worker are necessary and, further, a time required for the adjusting process is far from short. Moreover, the lens holder has to have a function of two mechanism elements of the optical path demarcating unit and the focus adjuster; therefore, it is difficult to achieve a small-sized lens holder in terms of its structure. Additionally, a mass-production is difficult since the lens holder is a mechanism element, whereby the percentage of the material cost in the production cost is high, thereby entailing an increased production cost.